US 7542651 B2
A cable assembly comprising a first fiber optic cable, a second fiber optic cable attached to the first fiber optic cable, and an apparatus for remotely releasing at least a portion of the second fiber optic cable from attachment to the first fiber optic cable. A cable assembly comprising a distribution cable, a tether cable attached and optically interconnected to the distribution cable at a first position, and removably attached to the distribution cable at one or more second positions, and a tether cable release apparatus for remotely releasing at least a portion of the tether cable from the distribution cable to allow the tether and a tethered assembly to be pulled to a predetermined location within a network.
1. A cable assembly, comprising:
a first fiber optic cable;
a second fiber optic cable attached to the first fiber optic cable; and
an apparatus for remotely releasing at least a portion of the second fiber optic cable from attachment to the first fiber optic cable, wherein the first and the second fiber optic cables are maintained together by at least one lashing.
2. The cable assembly of
3. The cable assembly of
4. The cable assembly of
5. The cable assembly of
6. A cable assembly, comprising:
a distribution cable;
a tether cable attached and optically interconnected to the distribution cable at a first position, and removably attached to the distribution cable at one or more second positions; and
a tether cable release apparatus for remotely releasing at least a portion of the tether cable from the distribution cable.
7. The cable assembly of
8. The cable assembly of
9. The cable assembly of
10. The cable assembly of
11. The cable assembly of
12. The cable assembly of
13. The cable assembly of
14. The cable assembly of
15. A cable assembly, comprising:
a distribution cable including a plurality of optical fibers and at least one access location positioned along the distribution cable wherein at least one pre-selected optical fiber of the distribution cable is accessed and terminated;
a tether including at least one optical fiber optically connected with the at least one pre-selected optical fiber of the distribution cable, wherein the tether is secured at a first end about the at least one access location and is releasably secured at one or more attachment positions along its length to the distribution cable; and
a tether release apparatus for releasing at least a portion of the tether from the distribution cable from a location remote from the one or more attachment positions.
16. The cable assembly of
17. The cable assembly of
18. The cable assembly of
19. The cable assembly of
20. A cable assembly, comprising:
a fiber optic distribution cable including a plurality of optical fibers and at least one access location for terminating and routing at least one pre-selected optical fiber away from the distribution cable;
a tether cable including at least one optical fiber optically connected to the at least one preselected optical fiber, the tether cable being releasably attached to the distribution cable at one or more attachment points; and an apparatus for releasing at least a portion of the tether cable from the distribution cable at a location remote from the one or more attachment points, wherein the apparatus includes a pull cord for releasing the one or more attachment points.
21. The cable assembly of
22. The cable assembly of
23. The cable assembly of
24. The cable assembly of
1. Field of the Invention
The present invention relates generally to various apparatus for remotely releasing tethered assemblies of fiber optic cable assemblies, and more specifically, to various apparatus for remotely releasing tethers and tethered assemblies interconnected at Flexible Network Access Points (“FlexNAP” or “FNAPP”) along a distribution cable in order to access the tethers and tethered assemblies at a vault, hand hole, man hole, other structure or remote location within an optical network.
2. Technical Background
In “Fiber-to-the-Premises” (FTTP) and other optical networks, referred to generically herein as “FTTx” networks, pre-engineered fiber optic distribution cables including FlexNAPs are being developed and deployed to facilitate the delivery of services to subscribers over a plug-and-play network. The most recently developed FlexNAP systems typically include distribution cables having pre-selected optical fibers terminated, also referred to herein as “pre-terminated”, and accessed from the distribution cable at an access point, and routed separately away from the distribution cable to provide branches, referred to herein as “tap points,” “mid-span access locations,” “branch points” or “tether attach points.” At these tap points, the pre-selected and pre-terminated optical fibers of the distribution cable are often spliced or otherwise optically connected to a length of optical cable referred to herein as a “tether.” The tether may terminate in a connection terminal, or may be used to provide optical fiber to an optical connection terminal, network interface device or other optical network terminal located within reach of the tether. The tether may also be used for mitigating span length measurement issues resulting from errors in pre-engineered cable assembly installations. The tether is typically lashed to the distribution cable during assembly and installation and released as needed.
Several methods for FlexNAP system deployment currently exist including, but not limited to, aerial drive-off, aerial pull-through, buried trench and buried duct installations. While early generations of closures were relatively large in diameter and inflexible to installation requirements, later and present generation closures include flexible overmolded solutions on the order of only about a few inches in both diameter and length, thus facilitating installation in both aerial and buried environments. With regard to buried installations in particular, installation within these environments is typically difficult because of diameter constraints and having to work within a closed environment. Installation is especially difficult through about 1.25 inch diameter ducts, a common diameter requirement of telecommunications service providers.
Current FlexNAP systems typically include one or more tethers having lengths ranging from about a few feet to several hundred feet in length. In small diameter buried duct environments, the tether typically terminates in a low-profile tethered assembly including at least one connector, for example a multi-fiber (Con2r-MT) connector available from Corning Cable Systems of Hickory, N.C. During installation within a buried duct environment, it is often necessary to access the tethered assembly at a vault, hand hole, man hole or other buried structure, commonly referred to herein as a “hand hole”, to connect the multi-fiber ferrule with another predetermined connector. Based on the number of tethered assemblies, varying tether lengths, locations of buried hand holes, the manner in which the FlexNAP system was installed and the engineering of the system itself, it is very difficult to ensure that each tethered assembly will be properly positioned and accessible at its predetermined hand hole. Most often, the distribution cable and only a portion of the tether length are visible at the hand hole, not the tethered assembly itself. Therefore, it is often necessary to detach or “unlash” the tether and tethered assembly from the distribution cable in order to pull the tether and tethered assembly back into the hand hole for access.
In aerial installation environments, the detachment of the tether may be as simple a process as going to each lashing location (where tape or tie-wraps are most commonly used) and removing or cutting each lashing along the length of the tether. In buried duct environments, this method of detaching the tether is much more difficult because of the lack of access to the lashings. Although it may be possible for an installation crew to manually remove the lashings by purposely overshooting each hand hole and then while pulling back to the proper position, remove the lashings as the distribution cable returns into the hand hole, this would be very manually labor intensive and require multiple operators working together from adjacent hand holes. Thus, what is needed is a way of releasing lashed tethers and tethered assemblies after cable assembly installation in order to allow the tethers and assemblies to be pulled into a hand hole or other buried structure for access. In particular, what is needed are remote tether release apparatus positioned along a cable along the length of the tether. Further, what is desired are remote tether release apparatus that allow a sufficient length of a tether to be released from the distribution cable from a hand hole at any point along the tether length, thus providing a cable assembly with a built-in feature for compensating for tap point placement errors that occur during system installation.
In one embodiment, the present invention provides various embodiments of tether release apparatus for cable assemblies including Flexible Network Access Points (FlexNAP) deployed in FTTx optical networks. The various tether release apparatus embodiments described herein allow a predetermined length of tether cable and its respective tethered assembly to be released from the distribution cable from a remote location along the length of the distribution cable away from the tethered assembly, thus facilitating tethered assembly access in installation environments, and in particular, buried duct environments at a hand hole. In other words, the tether cable may be released from a location remote from the tether's attachment point to its distribution cable. Remotely releasing the lashed tether and tethered assembly allows an improperly positioned tethered assembly to be released and pulled back into a hand hole for access without having the disturb or pull back the length of distribution cable. The released tether may also be routed to a desired location.
In another embodiment, the present invention provides tether release apparatus including a rip cord operable for tearing through tape or other lashing material used to lash the tether and tethered assembly to the distribution cable during cable installation. In one embodiment the ripcord may include, but is not limited to, a Kevlar reinforced thread or other ripcord material capable of withstanding installation and pulling forces. The ripcord and tape are installed in such a way as to secure the tether to the distribution cable while allowing the ripcord to be manually pulled through each lashing point. The ripcord may be wrapped around each lashing such that it tears through each lashing as it is pulled. A clamp or other anchor may be used to secure one end of the ripcord about the tap point. The ripcord may have a length about equal to or greater that the length of the tether, may run about parallel to the tether, and may be looped or otherwise wrapped around the lashings at predetermined positions along the tether length. To release the tether and tethered assembly, the ripcord may be pulled from a desired and convenient point, such as at a hand hole at which tethered assembly access is desired, and is pulled through the lashings. An alternative embodiment may include tying the ripcord around the tether as opposed to the distribution cable. Another embodiment may include a lashing cutting device that is pulled to cut the lashings and release the tether and tethered assembly.
In yet another embodiment, the present invention provides a remote tether release apparatus including a pull cord, and in some embodiments a pull rod, that runs about parallel to the tether and is anchored proximate the tap point at the upstream end and anchored about the tethered assembly at the downstream end. At the downstream end, the pull cord or rod is attached to a pin, spring, clip or other release apparatus suitable for releasing the anchored tethered assembly. The tether may be loosely held to the distribution cable using tape, tie-wraps or other fasteners that are torn, cut or released during tether detachment. Subsequent to cable assembly installation, an installer may access the pull cord in the hand hole or other location and pull it to release the pin, spring or clip maintaining the tethered assembly to the distribution cable. Once detached, the installer may then retract a portion of the tether length and the tethered assembly back through the duct, coil the slack within the hand hole and connect or reroute the tethered assembly as desired. If hand hole placement is missed all together, the distribution cable may be pulled in either a forward or backward direction in order to provide access to the tether release apparatus.
In yet another embodiment, the present invention provide tether release apparatus for FlexNAP systems including a distribution cable having at least one tap point and a tether attached/interconnected about the tap point. In one embodiment, the tether may terminate in a plug assembly including at least one connector. The tether release apparatus is anchored to the distribution cable about the tap point, runs parallel with the length of tether and is secured to plug assembly releasing structure about the plug assembly. The tether release apparatus may run about parallel to the distribution cable and may be secured at predetermined intervals along the distribution cable using clips, fasteners, corrugated tubing or other fastening means. In a specific embodiment, the tether release apparatus includes a multi-part clamp that tightens around the distribution cable as force is applied via a pulling apparatus. As the pulling apparatus is activated, force is applied through the clamp to a pulling/dust cap of the plug. As enough force is applied, the pulling/dust cap is released and the plug assembly is freed from the distribution cable. The tether may be secured to the distribution cable preferably using a non-adhesive wrapping material. A razor pull knife may be strung onto the pull cord and pulled underneath the wrapping material to slice it and release the tether cable.
In yet another embodiment, the present invention provides alternative tether release apparatus including, but not limited to, remote release clamps, pin releases, a solenoid actuated by applying a voltage across a trailing cable, cable actuated designs, overmolded junctions, and ratchet and pawl apparatus, among others. Alternative tether release apparatus may function to release a tethered plug assembly of other tethered assemblies from the distribution cable from a remote location in order to pull the assemblies to a predetermined location within the network.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description present exemplary embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the detailed description, serve to explain the principles and operations thereof. Additionally, the drawings and descriptions are meant to be illustrative and not limiting.
Reference will now be made in detail to the present preferred embodiments of the invention, and examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. Although various embodiments of apparatus for remotely releasing a tether and tethered plug assembly of a FlexNAP cable assembly are described and shown throughout the figures, it is envisioned that other tethered plug release apparatus designs may perform a similar function as applied to any cable assembly in which it is desired to remotely release a portion of the cable assembly, such as freeing one or more cables from other one or more cables. The term FlexNAP (“Flexible Network Access Point”) as used herein refers to a cable assembly including at least one flexible access point at which a pre-selected number of optical fibers are terminated and branched from the distribution cable. Throughout the specification and figures, the branched optical fibers are shown optically connected to a tether cable, the “tether”, terminating in a plug assembly including at least one single fiber or multi-fiber connector. In alternative embodiments, the tether may terminate in splice ready optical fibers, a connection terminal or any other structure for presenting optical fibers of the tether for interconnection. The tether is preferably remotely released to facilitate access to the tether and plug assembly at a convenient access location within the network away from the plug assemblies location resulting from installation.
Components of the remote release apparatus further include a pull cord 120 anchored at one end about the flexible body 108 and anchored at the other end about a rod 122. The pull cord 120 is sufficiently flexible and strong enough to withstand installation forces and preferably does not decrease the ability of the cable assembly 100 to flex during installation. For a cable assembly including about a 50 foot tether length, the pull cord 120 portion of the remote release apparatus runs the majority of the tether length, with the pull rod 122 running only a few feet of the tether length. The pull rod 122 may also be flexible, and the pull cord 120 preferably being more flexible than the pull rod 122. The tether 102 is routed about parallel to the distribution cable 106 and is lashed or otherwise fastened to the distribution cable at various intervals along the cables length using tie-wraps, tape, a wrapping, corrugated tubing or other suitable fasteners or lashes. As shown, the cable assembly 100 includes tape 124 at various positions along the pull cord length, and plastic fasteners 126 at various positions along the pull rod length. During remote release operation, as the pull cord 120 is pulled, the pull rod 122 is also pulled and slides through loops or other features of the fasteners 126, thus releasing the fasteners and the plug assembly 104. In other words, the fasteners 126 are held in position by the pull rod 126 and are released as the pull rod 126 is pulled through them. The pull cord 120 and/or pull rod 122 may further include a tape cutting device (not shown) for cutting the tape 124 as the device is pulled along the cable length. The pull rod 122 is removably secured in place at the downstream end either under the anchor 118 or by a heat shrink, tape or other pull rod securing component 128. Referring specifically to
The remote tether release apparatus includes a multi-part clamp 402, wherein a wedge-sliding action of the clamp 402 causes portions 404 and 406 to tighten around the distribution cable 106 as pulling force is applied to a pull cord 120. The pull cord 120 has a length about equal to the length of the tether 102 and runs about parallel to the tether. The pull cord 120 is secured to the distribution cable 106 using clips 408 or other like fasteners. As shown, the clips 408 are not secured around the tether 102, thus as the pull cord 120 is pulled the plug assembly 104 is released from attachment and the tether 102 and plug assembly 104 can be pulled back to the hand hole. In an alternative embodiment, the clips 408 may also be secured around the tether 102 and released as the pull cord 120 is pulled. The pull cord 120 may also be used to apply a clamping force to the clamp 402, holding it in place, while the plug assembly 104 is pulled loose of the clamp 402 by pulling on the tether 102. As shown in
While various embodiments for remote tether release have been shown, alternative designs may exist for performing the same or similar function. It is intended that the present invention cover such alternative embodiments. In addition, although remote tether release has been shown as applied to pre-engineered fiber optic cable assemblies, it is envisioned that the methods and apparatus may be applied to any cable assembly in which it is desired to remotely release at least one cable from another cable. It is apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.